Cloud computing is generally defined as a form of computing in which dynamic and/or virtualized resources are provided as services over a distributed network of physical computing machines or servers, such as the Internet. Client processes, software applications, and users thereof, are not required to have explicit knowledge or control over the technology infrastructure within the cloud. Instead, they can request or call upon services from the cloud, which are then provided by other providers within the cloud. As such, cloud computing promises software application developers with an easy means way of deploying their application to run simultaneously upon thousands of servers in a cloud.
To date, different solutions of deploying software applications in a cloud have emerged that are generally cloud specific, i.e. the applications need to conform to a cloud/hypervisor specific application program interface (API) to run on their servers. Using this methodology, it is not easy for a cloud customer to migrate an application from one cloud provider to another cloud provider. Cloud providers can address this problem somewhat by offering hypervisors in their clouds. Generally, a hypervisor acts as a layer between a server's hardware and its operating system. This provides an abstraction layer that allows each physical server to run one or more virtual servers, and effectively decouples the operating system and its applications from the underlying physical server. When used in a cloud, the cloud customer can supply a virtual machine image which contains the customer application to the hypervisor. The image will then be booted in potentially thousands of hypervisors in the cloud. Since there are generally only a few hypervisor types this approach standardizes the format for how the application developer has to package the application. Instead of creating a standalone application that fits into a specific cloud API, the developer now has to create a suitable virtual machine image.
However, such a created virtual machine image can be large, depending on the Java application contained therein. The image can also grow in size when the virtual machine image is executed. For example, application generated data and log files can be stored within the image, and such an image can grow to several gigabytes in size. Since it is usually unavoidable that the Java application or the Java virtual machine (JVM) contained within the virtual machine image will have to be updated there is a need for a tool that can efficiently update such a virtual server image and do so without disturbing the accumulated application data.